Sorry to sound negative but do you realise that using the G540 with those motors your not actually getting 3Nm holding torque.? The G540 is limited to 3.5A and those motors are 4.2A so you'll have a proportional loss of torque.!! . . basicly you'll only have 83% motors rated torque so the potential issues could be worse.!!

Not trying to put a downer on the build and fully understand the need to keep funds under control just want to high-light potential areas for disapointment when finished.
Unfortunatly I see far too much Miss-match motor-drive-PSU combo's and one of the things I hate when speaking to new users is telling them they have bought mis-matched stuff.

I say bo@#*cks to the kitchen sell the GF buy some big drives. .